Telephone transmitter



(No' Model.)

0., E. EGAN. v TELEPHONE TRANSMITEER. No. 355,686., Patented Jan. 11,1887;.-

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m I I UN ii STATES CHARLES E. EGAN, OF COLUMBUS,

OHIO, ASSIGNOR OF ONE-HALF TO w. Y. MILES, OF'SAME PLACE.

TELEPHONE-TRANSMITTER.

SPECIFICATION forming part of Letters Patent No. 355,686, dated January11, 1887.

Application filed April 6, 1886. Serial No. 197,965. (No model.)

To all whom it may concern.-

Be it known that I, OHARLEsE. EGAN, of Columbus, in the county ofFranklin and State of Ohio, have invented certain new and usefulImprovements in Telephone-Transmitters; and I do hereby declare that thefollowing is a full, clear, and exact description of the invention,which will enable others skilled in the art to which it appertains tomake and use the same, reference being had to the accompanying drawings,and to the letters of reference marked thereon, which form part of thisspecification.

My invention relates to telephonic transmitters which operatev byvarying the resistance in an electric current; and it consists moreespecially in new and improved means ofmounting the carbon electrode,wherebya more delicate contact is possible than has heretofore beenattained.

It also consists in improvementsin other details,which will befullydescribed hereinafter,

' and more particularly pointed out in the claims.

Referring to the drawings accompanying this specification, Figure l is asection of my transmitter-box and portions of the apparatus. Fig. 2 is adetail view showing one of the electrodes.

The same letters indicate like parts in both figures.

A is the diaphragm, which is secured by screwsor pins cato the innerside of the door of the transmitter-box, as usual. Through an opening inthe center of the diaphragm passes a screw, o,which is tapped into abrass block, B, behind the diaphragm. Between the diaphragm and theblock B is a cushion consisting of a spiral spring, 0, one end of whichis soldered to the diaphragm and'the other to the block. By means of thescrew a the tension of spring 0 may be adjusted. The block B enters thespring or is partly surrounded by the same, and it has a screw-socket ofthe properlength.

The carbon electrode D is secured to the block 13 by means of pinsd d.This electrode has considerable surface, and makes contact at severalpoints with the opposite electrode, E, which consists of a metallicplate, F, carrying the thumb-screwsffff. Fourof these thumb-screws areshown in the drawings; but the number may be varied as desired. Eachthumb-screw is provided with a platinumtip, p, which makes contact withthe carbon electrode D. The plate Fis fastened at f to a metallicspring, G, which is secured to a post, H, projecting from the upper partof the door of the transmitter-box.

The remaining parts of my transmitter are those already well known andin common useviz., an induction-coil, I, the primary of which isconnected through the binding posts J J with the battery K, and thesecondary with the line binding-posts L L.

The circuit from battery K is by way of the binding-post J, to spring G,to electrode E and its contact-points p p, to carbon electrode.

D, block B, spring 0, diaphragm A, to primary of coil I, binding'post J,to battery.

I find that with the above-described construction the normal contactbetween the electrodes is firm and complete, while the varia tions ofcontact produced by the vibrations of the diaphragm when the instrumentis used correspond perfectly with said vibrations, Without so muchdanger of breaking the circuit as in transmitters which lack mycushioning support for the carbon electrode.

The contact between the electrodes is capable of ready and delicate adjustment by means of the screw a'and the thumb-screws ffff, while theplace of contact can be varied by turning the plate F on the pivotf, soas to bring the platinum points 1) opposite a fresh surface of carbon.

. What I claim, and desire to secure by Let ters Patent, is

* 1. In a tclephone-transmitter,the combina tion of the diaphragmhavinga helicalspringo cushion and ascrew-stem secured thereto, and anelectrode connected with said spring-cushion and adjustably fitted onthe screw-stenr carried by the electrode, with a tension-regulator ordevice or movable electrode bearing upon the diaphragm electrode, andsuitable circuit and battery connections, substantially as herein setforth.

2. In a telephone-transmitter, the combination of the diaphragm carryinga helical a, and electrode E,

5 The combination, with the diaphragm A and carbon electrode D, of plateF, carrying 1 contact-screws f fr and pivoted at f to supporting-springG, whereby the plate can be turned .to vary the position of thecontactpoints.

In testimony that I claim the foregoing as 20 my own I affix mysignature in presence of two witnesses.

' CHARLES E. EGAN. Witnesses:

O. E. DUFFY,

S. BRASHEARS.

